Coordinated multi-point transmission/reception (CoMP) is already recognized as a very efficient method for extending the coverage of a high-speed data service, improving the throughput at a cell boundary, and increasing the average throughput of the system in a mobile network. In coordinated multi-point transmission/reception, it is required that clustering be performed for all network nodes that participate in the cooperation and a network node in each cluster offers the coordinated multipoint service to multiple terminals. FIG. 1 is a diagram showing a simple multi-BSs coordination service scene in a conventional mobile network. In FIG. 1, two base stations, base station 1 and base station 2, coordinate with each other to provide services to terminal 1 and terminal 2 at the same time. In a practical application, two or more base stations sometimes provide services to two or more terminals at the same time.
3GPP, an international standardization organization, developed the system architecture and the specifications of the second-generation and third-generation mobile communication network, and those specifications are already used today for networks that use the air interface. 3GPP is now working on establishing standards for Long Term Evolution-advanced (LTE-advanced) for a fourth-generation mobile communication network. In the standard establishment process of LTE-advanced, coordinated multi-point transmission/reception is already employed as a service of the multi-BSs coordination service.
FIG. 2 is a diagram showing the frame of the multi-BSs coordination service system that performs centralized control in the conventional technology. In the description below, the LTE-advanced network established by the 3GPP standardization organization is used an example of application. The facility and the method of this network may be applied to other mobile networks that support the multi-BSs coordination service. In this typical frame, the mobile cellular network is composed of at least multiple base stations. The multiple base stations connect to one base station controller (or multiple base station controllers in an actual application), which negotiates about the key parameters of the multi-BSs coordination service. The access network connects the base station controller and the base stations to the mobile network gateway. The mobile network gateway, connected to the Internet or other servers, acts as an end node of the entire mobile access network. The mobile network gateway at least provides the information, received from other servers and the Internet, to all mobile terminals and at least performs processing, such as network registration, security, and cost calculation, for all mobile terminals.
The multi-BSs coordination service has many advantages. However, for each base station to select the optimal base station cluster dynamically and individually, a large amount of data and channel state information must be shared among all base stations. This greatly increases the load of communication among base stations and, at the same time, requires the base stations to implement a complicated algorithm for selecting the optimal cluster. In addition, to select the optimal base station cluster, a large amount of information must be shared between base stations and between a base station and a terminal. This significantly consumes the signaling and resources and decreases the power of the mobile network.
From another viewpoint, if static base station clustering is used in the multi-BSs coordination service such as that shown in FIG. 3, the consumption of the signaling and resources can be saved. However, because the mobile terminal locations and the service channel state are constantly changing in a mobile network, it is difficult to satisfy all the needs of the multi-BSs coordination transmission by selecting static optimal-base station clustering. Simple static base station clustering, though simple, prevents the air interface utilization from being increased using the multi-BSs coordination service, making the multi-BSs coordination service meaningless.
FIG. 3 is a diagram showing an example of static clustering in the conventional multi-BSs coordination service. In the figure, multiple base stations 1-30 are installed in the network, and the base stations are divided statistically into multiple base station clusters with three base stations in each cluster. When the multi-BSs coordination service is performed, only three base stations in a cluster can coordinate with each other but the coordination service cannot be performed across clusters. The advantage of this configuration is that the consumption of a base station caused by dynamic clustering is reduced. In this case, however, the performance cannot reach the optimal level. If a mobile terminal is located around the cell boundary of several base stations in the same base station cluster, the mobile terminal can receive the benefit from the multi-BSs coordination service. If a mobile terminal is located around the boundary between two base stations, for example, around the boundary between the neighboring cells of the base station 2 and the base station 4 in FIG. 3, the base station 2 and the base station 4 cannot perform the multi-BSs coordination service because of the static clustering rule. Therefore, even if these two base stations have enough resources and good channel quality, the mobile terminal cannot receive such a service. Those situations described above are disadvantageous for optimally using the radio air-interface resources of a base station.
In summary, a simpler, lower-consumption solution for selecting dynamic base station clustering is required in a mobile network that supports multi-BSs coordination transmission. The solution is required to find the optimal base station clustering result more quickly and, at the same time, to reduce the consumption of the signaling and resources for calculating base station clustering.
Patent Literature 1 and Patent literature 2 disclose a method that, before the communication between a cluster, composed of multiple radio nodes, and the node at the other end of communication is started, they communicate with each other to negotiate about multi-node coordination communication. However, those nodes are all terminal nodes and the mobile communication base station does not participate in clustering.
Patent Literature 3 discloses a method that the antenna units from two or more base stations configure a multi-antenna array. However, in this patent, the base station cluster is already established and a detailed clustering method is not mentioned.
Patent Literature 4 discloses a method that two transmission nodes coordinate with each other to communicate with one reception node, but the detailed contents of the clustering algorithm is not mentioned.